Police in four European countries have busted a human trafficking ring involving Bulgarian women used as sex workers, continental police and prosecution agencies Europol and Eurojust said today.

"France, Bulgaria, Poland and Belgium joined forces to dismantle a criminal network involving trafficking of human beings," the agencies Eurojust said in a joint statement in The Hague.

"Young women were recruited in Bulgaria for the purpose of sexual exploitation in several European countries including Belgium and France," the agencies said, adding proceeds from the gang's activities were sent back to Bulgaria and "invested".

Police based in the southeastern French city of Lyon, together with the anti-trafficking central police agency opened an investigation in October 2010.

Nine suspects were arrested in France, Belgium, Poland and Bulgaria after European arrest warrants were issued at the request of French authorities.

Thirteen searches were also done and mobile phones were seized during the operation, conducted with the support of a coordination centre run by Eurojust's French Desk, the statement said.